DNA encoding a truncated pneumogoccal surface protein (PspA)

ABSTRACT

A purified pneumococcal surface protein A (PspA) comprises a truncated form of the PspA protein which is immunoprotective and contains the protective epitopes of PspA. The PspA protein is soluble in physiologic solution and lacks at least the cell membrane anchor region of the whole protein. The protein is formed by insertion-duplication of mutagenesis of S. pneumoniae with pspA gene and expression of the truncated protein into the growth medium.

REFERENCE TO RELATED APPLICATION

This application is continuation of application Ser. No. 07/835,698, filed Feb. 12, 1992, now abandoned, which is a continuation-in-part of copending U.S. patent application Ser. No. 656,773 filed Feb. 15, 1991, now abandoned.

FIELD OF INVENTION

The present invention is concerned with the development of an improved vaccine against pneumococcal infections.

BACKGROUND TO THE INVENTION

Streptococcus pneumoniae is an important cause of otitis media, meningitis, bacteremia and pneumonia. Despite the use of antibiotics and vaccines, the prevalence of pneumococcal infections has declined little over the last twenty-five years.

It is generally accepted that immunity to Streptococcus oneumoniae can be mediated by specific antibodies against the polysaccharide capsule of the pneumococcus. However, neonates and young children fail to make an immune response against polysaccharide antigens and can have repeated infections involving the same capsular serotype.

One approach to immunizing infants against a number of encapsulated bacteria is to conjugate the capsular polysaccharide antigens to protein to make them immunogenic. This approach has been successful, for example, with Haemophilus influenzae b (see U.S. Pat. No. 4,496,538 to Gordon and U.S. Pat. No. 4,673,574 to Anderson). However, there are over eighty known capsular serotypes of S. pneumoniae of which twenty-three account for most of the disease. For a pneumococcal polysaccharide-protein conjugate to be successful, the capsular types responsible for most pneumococcal infections would have to be made adequately immunogenic. This approach may be difficult, because the twenty-three polysaccharides included in the presently-available vaccine are not all adequately immunogenic, even in adults.

An alternative approach for protecting children, and also the elderly, from pneumococcal infection would be to identify protein antigens that could elicit protective immune responses. Such proteins may serve as a vaccine by themselves, may be used in conjunction with successful polysaccharide-protein conjugates, or as carriers for polysaccharides.

In McDaniel et al (I), J.Exp.Med. 160:386-397, 1984, there is described the production of hybridoma antibodies that recognize cell surface polypeptide(s) on S. pneumoniae and protection of mice from infection with certain strains of encapsulated pneumococci by such antibodies. This surface protein antigen has been termed "pneumococcal surface protein A" or PspA for short.

In McDaniel et al (II), Microbial Pathogenesis 1:519-531, 1986, there are described studies on the characterization of the PspA. Considerable diversity in the PspA molecule in different strains was found, as were differences in the epitopes recognized by different antibodies.

In McDaniel et al (III), J.Exp.Med. 165:381-394, 1987, there is disclosed that immunization of X-linked immunodeficient (XID) mice with non-encapsulated pneumococci expressing PspA, but not isogenic pneumococci lacking PspA, protects mice from subsequent fatal infection with pneumococci.

In McDaniel et al (IV), Infect. Immun., 59:222-228, 1991, there is described immunization of mice with a recombinant full length fragment of PspA that is able to elicit protection against pneumococcal strains of capsular types 6A and 3.

In Crain et al, Infect.Immun., 56:3293-3299, 1990, there is described a rabbit antiserum that detects PspA in 100% (n=95) of clinical and laboratory isolates of strains of S. pneumoniae. When reacted with seven monoclonal antibodies to PspA, fifty-seven S. pneumoniae isolates exhibited thirty-one different patterns of reactivity.

The PspA protein type is independent of capsular type. It would seem that genetic mutation or exchange in the environment has allowed for the development of a large pool of strains which are highly diverse with respect to capsule, PspA, and possibly other molecules with variable structures. Variability of PspA's from different strains also is evident in their molecular weights, which range from 67 to 99 kD. The observed differences are stably inherited and are not the result of protein degradation.

Immunization with a partially purified PspA from a recombinant λ gt11 clone, elicited protection against challenge with several S. pneumoniae strains representing different capsular and PspA types, as described in McDaniel et al (IV), Infect. Immun. 59:222-228, 1991. Although clones expressing PspA were constructed according to that paper, the product was insoluble and isolation from cell fragments following lysis was not possible.

While the protein is variable in structure between different pneumococcal strains, numerous cross-reactions exist between all PspA's, suggesting that sufficient common epitopes may be present to allow a single PspA or at least a small number of PspA's to elicit protection against a large number of S. pneumoniae strains.

In addition to the published literature specifically referred to above, the inventors, in conjunction with co-workers, have published further details concerning PspA's, as follows:

1. Abstracts of 89th Annual Meeting of the American Society for Microbiology, p. 125, item D-257, May 1989;

2. Abstracts of 90th Annual Meeting of the American Society for Microbiology, p. 98, item D-106, May 1990;

3. Abstracts of 3rd International ASM Conference on Streptococcal Genetics, p. 11, item 12, June 1990;

4. Talkington et al, Infect. Immun. 59:1285-1289, 1991;

5. Yother et al, J. Bacteriol. 174:601-609, 1992; and

6. Yother et al, J. Bacteriol. 174:610-618, 1992. The latter three publications occurred after the filing of the aforesaid U.S. Ser. No. 656,773.

In the specification which follows and the drawings accompanying the same, there are utilized certain accepted abbreviations with respect to the amino acids represented thereby. The following Table I identifies those abbreviations:

                  TABLE I                                                          ______________________________________                                         AMINO ACID ABBREVIATIONS                                                       ______________________________________                                         A = Ala = Alanine  M = Met = Methionine                                        C = Cys = Cysteine N = Asn = Asparagine                                        D = Asp = Aspartic Acid                                                                           P = Pro = Proline                                           E = Glu = Glutamic Acid                                                                           Q = Gln = Glutamine                                         F = Phe = Phenylalanine                                                                           R = Arg = Arginine                                          G = Gly = Glycine  S = Ser = Serine                                            H = His = Histidine                                                                               T = Thr = Threonine                                         I = Ile = Isoleucine                                                                              V = Val = Valine                                            K = Lys = Lysine   W = Try = Tryptophan                                        L = Leu = Leucine  Y = Tyr = Tyrosine                                          ______________________________________                                    

SUMMARY OF INVENTION

The present invention relates to the preparation of mutants of S. pneumaniae that secrete an immunogenic truncated form of the PspA protein, and isolation and purification of the secreted protein. The truncated form of the PspA protein is immunoprotective and contains the protective epitopes of PspA. The PspA protein is soluble in physiologic solution and lacking at least the functional cell membrane anchor region.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic representation of the domains of the mature PspA;

FIG. 2 is the N-terminal amino acid sequence of PspA (see SEQ ID NO.3), wherein bold upper case letters denote charged hydrophilic amino acids, lower-case letters designate apolar, hydrophobic residues, and underlined bold lower case letters denote uncharged, polar, hydrophilic residues;

FIG. 3A-B is the DNA sequence of the pSpA gene (see SEQ ID NO.1) with deduced amino acid sequence for the PspA protein (see SEQ ID NO.2);

FIG. 4A-B depicts the restriction map of pspA (FIG. 4A) and the use of insertion-duplication mutagenesis to construct mutations in the pSpA gene (FIG. 4B),

FIG. 5 shows the deduced amino acid sequence for the N-terminal region of PspA (see SEQ ID NO.4) and the general location of epitopes recognized by monoclonal antibodies;

FIG. 6 shows antibody reactivity with PspA fragments produced by various pspa gene segments; and

FIG. 7 shows the mapped location of epitopes in the PspA fragments produced by the different pSpA gene segments.

GENERAL DESCRIPTION OF INVENTION

According to one aspect of the present invention, there is provided a purified immunoprotective pneumacoccal surface protein, comprising a truncated form of PspA which contains the immunoprotective epitopes of the protein and up to about 90% of the whole PspA protein and from which the functional cell membrane anchor region is absent.

Through the technique of insertion-duplication mutagenesis of the psna gene of the strain Rx1 of Streptococcus pneumoniae with plasmids containing cloned fragments of the pspA structural gene, it has been possible to produce soluble fragments of PspA that are secreted by pneumococci.

In another aspect of the present invention, therefore, there is provided a method of forming an immunoprotective truncated PspA protein, which comprises effecting insertion-duplication mutagenesis of a bacterium with a pspA gene resulting in the coding of a truncated expressible PspA protein, growing the mutated bacterium to effect expression of a truncated PspA protein, and isolating the protein.

The molecular size of the purified truncated PspA protein obtained may be varied by directing the point of insertion, which determines the termination of gene expression, to different points in the pspA gene. For example, an N-terminal fragment of apparent molecular weight of 43 kD, constituting approximately one-half of the native protein, has been found useful.

The truncated segment which is produced by this procedure is capable of eliciting protection in mice from fatal challenge with type 3 S. pneumoniael, demonstrating for the first time that a purified PspA can elicit protection and that this truncated segment of the protein contains protective epitopes of PspA.

Amino acid sequence information was obtained on the N-terminal 45 amino acids of the truncated segment of PspA. This sequence is shown in FIG. 2 SEQ ID NO:3. Predictive secondary structural analysis shows that this sequence has a very strong alpha-helical formation, with no non-helical inserts. About 51% of the segment is composed only of two amino acids, namely lysine, a charged amino acid, and alanine, a non-polar amino acid.

Analysis of this 45-amino acid sequence also reveals that it contains a seven-residue periodicity (see FIG. 2) SEQ ID NO:3. In PspA, the periodicity begins with residue 8 and extends throughout the entire sequence, for nearly eleven turns of the helix. Positions "a" and "d" are occupied by apolar amino acids and position "b", "c" and "f" generally contain hydrophilic amino acids. Position "f" is predominantly occupied by lysine. Having regard to these observations, this region of PspA is very likely in an alpha-helical coiled-coil configuration. The deduced amino acid sequence for the whole of the α-helical coiled-coil region is shown in FIG. 5 SEQ ID NO:4.

We also have cloned and sequenced the entire coding region of pspA (see FIG. 3A-B) SEQ ID NO:1. The deduced amino acid sequence for the PspA protein reveals three distinct regions of the PspA molecule, shown schematically in FIG. 1. Accordingly, a further aspect of the present invention, there is provided a biologically-pure recombinant DNA molecule coding for the PspA protein or portions thereof and having a coding sequence included within set forth in FIG. 3 SEQ ID NO:1or having substantial homology thereto.

The DNA sequence of the pspA gene is contained on a HindIII - KpnI fragment that is 2086 base pairs in length. The pspA gene itself represents approximately 1985 base pairs of this fragment, and comprises an initial region containing transcription and translational signals with translation starting at the ATG/met (nucleotide position 127, codon position -31), followed by a leader sequence extending from the AAG/met (nucleotide position 127, codon position -31) to CGA/ala (nucleotide position 217, codon -1). Mature Pspa starts with the glu amino acid at nucleotide position 220 (codon +1) and ends at the translational stop TAA/OCH at nucleotide position 1984. This translational stop cadon is followed by transcription termination signals.

The amino terminal of the protein sequence, predicted from the DNA sequence of FIG. 3A-B SEQ ID NO:2, contains a 31 amino acid leader sequence and a 45 amino acid sequence identical to the 45 amino acid sequence of the N-terminal of PspA (FIG. 2 SEQ ID NO:3). The amino end of the predicted protein sequence is highly charged and α-helical in nature. This region has homology with tropomyosin at the amino acid level (approximately 22% identity and 50% similarity). This homology is due largely to a repeating seven residue periodicity where the first and fourth amino acids are hydrophobic, the intervening amino acids are helix-promoting and the seventh amino acid is charged. This pattern is consistent with that of an α-helical coiled-coil molecule and indicates that the α-helical coil extends through the N-terminal half of the molecule. The amino acid sequence of the whole of the α-helical coil region is shown in FIG. 5 SEQ ID NO:4.

Following the charged helical region is a proline-rich region in which 23 of 81 amino acids are prolines. Immediately carboxy to the proline-rich region is the first of ten highly homologous twenty amino acid repeats. The only significantly hydrophobic region in the sequenced portion of the molecule begins at the last repeat. This potential membrane-spanning region contains several charged amino acids preceding the translational stop codon.

The insertionally-inactivated mutants of S. pneumoniae lacking the C-terminal anchor regions are capable of growth in chemically-defined medium and secrete the N-terminal portion of the PspA protein into the medium. The N-terminal region of PspA is highly soluble in the culture medium and is much easier to isolate than the entire molecule. Soluble truncated molecules have been produced using insertional duplicational mutagenesis directed by the cloned PspA DNA fragments shown in FIG. 4A-B. Expression of the same truncated construct (with the pneumococcal promoter) in E.coli results in the same PspA fragment being secreted into the periplasm of E.coli. PspA is readily released from the periplasm by hypotonic lysis.

Truncated PspA is isolated from culture medium of mutant pneumococci in any convenient manner, such as by tangential flow filtration. Ion-exchange chromatography then is performed on an anionic resin to purify the protein. In this procedure, the solution containing PspA is dialyzed to pH6 in 0.02 M salt solution and passed over the resin. The PspA is eluted from the resin with a gradient of 0.08 to 2.0 M ionic strength and is collected in the fraction between 0.34 and 0.87 M ionic strength, depending on the nature of the column used.

The PspA may be further purified by sodium dodecyl sulfate polyacrylamide gel (SDS-PAGE) electrophoresis. The PspA-containing portion of the gel is identified by staining of the gel and PspA is electroeluted from this portion.

The electrophoresis purification is convenient when only small quantities of PspA are being handled. As an alternative, more suited to large-scale production, the protein may be purified by size chromatography in a pH7 phosphate buffer.

Since it is possible to obtain expression of the truncated form of PspA into the culture medium, as opposed to it being trapped within the cell wall and making purification much more complicated, it is possible to isolate other proteins that have been cloned into the truncated pspA gene by making fusion proteins between pspA and other proteins. Such a technique may be employed to enhance the immunogenicity or preserve the immunogenic structural conformation or presentation of the gene product, to permit the fusion protein to be used in immunization, which may be systemic and/or mucosal, against disease.

One example of such a fusion protein is a fusion of the soluble N-terminal region of PspA and the B-subunit of cholera toxin. Fusion proteins also may be formed by chemical attachment of the truncated PspA protein to other proteins.

Another aspect of the present invention, therefore, provides a method for the production of cloned proteins, which comprises fusing a pspA gene coding for a truncated form of PspA protein with the gene coding for another protein to form a fusion protein clone, transforming S.pneumoniae, E.coli or other bacteria with the fusion protein clone, growing the transformed bacterium to effect expression of a fusion protein comprising truncated PspA and the other protein into the culture medium, and isolating the fusion protein.

By using this technique, there can be produced cloned proteins in gram positive bacteria, such as pneumococci, for example, S.pneumoniae, and mycobacteria, for example, Bacille Calmette-Guerin (BCG). This approach overcomes the problems inherent in the production of proteins in gram negative bacteria, such as E. coli, usually used for cloning, in particular the need to purify the recombinant proteins from endotoxin and the toxicity of many gram positive DNA sequences in gram negative organisms.

For the expression of a fusion protein comprising the soluble N-terminal region of PspA and the B-subunit of cholera toxin (CTB), a gene fusion of a pspA gene coding for a truncated form of PspA protein with a ctxB gene coding for the B-subunit of cholera toxin is effected. Following expression of the fusion protein, the PspA and CTB may be cleaved one from another by dilute acid at an asparagine-proline sequence, known to be labile to dilute acid, engineered at the fusion site of the two proteins.

CTB is known to be highly specific for monosinlaganglioside (G_(M1)). Accordingly, the fusion PspA-CTB protein may be isolated from the culture medium by adsorption to a G_(M1) affinity column, from which the fusion protein subsequently may be eluted at low pH.

The PspA-CTB fusion protein finds considerable utility in solid phase immunoadsorbant assays. By using the fusion protein, it is possible to coat solid supports, such as microtitration plates, with PspA fragments without having first to isolate the PspA fragments. This may be done by adding bacterial extract containing the fusion protein to plates coated with G_(M1). The PspA-CTB fusion protein then binds to G_(M1) through the CTB moiety, thereby coating the solid support with PspA. The resulting coated product then may be used in a solid phase immunoadsorbant assay for the detection of PspA antibody and/or antigen in test samples. Such immunoadsorbant assays constitute an additional aspect of this invention.

The PspA attachment/anchor region, containing the proline-rich region, the repeat region and/or the C-terminus of PspA, also may be employed to effect expression of heterologous proteins in pneumocacci, or other gram positive or gram negative bacteria in the which the attachment/anchor region is functional. Generally, expression is effected on bacterial membrane, cell walls or cell surfaces in gram positive bacteria and in the periplasm of gram negative bacteria. An example of such heterologous protein is the B-subunit of cholera toxin.

As mentioned above, the truncated form of PspA provided herein contains the immunoprotective epitopes of the protein and hence is useful in a vaccine against pneumococcal infection. Accordingly, a yet further aspect of the present invention provides a vaccine against pneumococcal infection comprising, as an immunogenically-active component, the purified immunoprotective pneumococcal surf ace protein provided herein. The PspA protein may be employed as one component of a multicamponent vaccine which is effective in providing protection from a variety of infections.

In addition, gram positive bacteria which have been transformed to express the pspA gene coding for the truncated soluble PspA protein may be employed, in a live-attenuated or killed form, as an immunologically-active component of a vaccine against pneumococcal infection. In the transformed bacterium, such pspA gene may be fused to a gene coding for another protein. Accordingly, an additional aspect of this invention provides a vaccine against pneumococcal infection comprising, as an immunologically-active component, a live-attenuated or killed bacteria containing a gene coding for the truncated form of PspA.

The truncated form of PspA also may be employed in conjugates with normally weakly-immunogenic or non-immunogenic protection-eliciting molecules, such as various polysaccharides, to achieve immunogenic potentiation thereof. An additional aspect of the invention, therefore, provides a vaccine comprising, as an immunogenically-active component, a conjugate of the purified immunoprotective pneumococcal surface protein provided herein and a normally weakly-immunogenic or non-immunogenic protection-eliciting molecule.

Conserved sequences of pspA, particularly those in the proline-rich and/or repeat regions of the gene, may be employed as probes to detect the presence of pneumococci of various strains, through detection of pneumococcal DNA, in tissues, body fluids and/or secretions. Similarly, portions of the pspA gene may be used in diagnostic kits for the detection of pneumococcal infections.

In addition, primers made based on conserved sequences of pspA, particularly those in the proline-rich and/or repeat regions, may be used to assay for the presence of pneumocacci in tissues, body fluids and/or secretions, through amplification of pneumococcal DNA. In this regard, a single primer pair derived from the nucleotide sequence of the pspa gene of S.pneumoniae may be employed in an assay using the polymerase chain reaction (PCR) for the specific detection of Streptococcus pneumoniae.

Specific amplification has been achieved of a 678 base pair DNA fragment from S.pneumoniae strain Rx1. After 30 cycles of amplification, the amplimer was detectable by agarose gel electrophoresis. The fragment was successfully amplified in all 32 strains of S.Pneumoniae tested. PCR DNA amplification was able to detect less than an estimated 20 ficograms total genomic pneumococcal DNA.

Primers LSM1 and LSM2, having the nucleotide sequences:

LSM1 5'-CCGGATCCAGCTCCTGCACCAAAAC-3' (see SEQ ID NO.5)

LSM2 5' -GCGCTGCGACGGCTTAAACCCATTCACCATTGG-3' (see SEQ ID NO.6)

amplified the 678 base pair product from pspA from nucleotides 1312 to 1990 of the Rx1 pspA sequence (FIG. 3A-B).

The PCR analysis using the primers described herein is performed in accordance with conventional PCR techniques, such as are described in the literature, for example, as described in Arnhem et al at C&EN Special Report, 36, Oct. 1, 1990. For detection purposes, the primer may be labelled or labelled nucleotide triphosphates may be included in the PCR reaction to label the PCR amplification product.

The PCR primers may be prepared by well-known methods, for example, by oligonucleotide synthesis or by fragmentation of a larger nucleotide sequence using suitable restriction enzymes.

The ability to use a single primer capable of detecting a large number of S.pneumoniae strains enables a universal PCR detection kit to be provided which is able to diagnose pneumococcal infection in mammals, including humans, independent of the strain which has caused the disease.

EXAMPLES Example 1

This Example illustrates the preparation and growth of novel strains of S. pneumoniae.

The S. pneumoniae strain Rx1, which is a non-encapsulated derivative of capsular type 2 strain D39 (National Collection of Type Cultures, London, NCTC #7466), was subjected to insertional inactivation (as described in McDaniel et al (III) 1987, Crain et al 1990, Talkington et al 1991, with 10 different cloned fragments of PspA (see FIG. 4A-B). These fragments have all been obtained from restriction digests of cloned PspA DNA on a plasmid in E.coli strain JY4313 (deposited with the American Type Culture Collection on Jan. 31, 1991 under ATCC accession number 68529). This insertional duplication mutagenesis (see FIG. 4A-B) results in the termination of gene expression near the 3' end of the cloned fragment.

One of the resultant strains, JY2008 (deposited with the American Type Culture Collection on Jan. 24, 1991 under accession number 55143), which was produced by a fragment of DNA encoded in pKSD300 (McDaniel et al (III) 1987), produces a PspA fragment of 27 kDa (apparent molecular weight 43 kDa) . This fragment is approximately 40% the size of the native 65 kDa (84 kDa apparent size) protein.

The expected molecular size is based on the deduced amino acid sequence and the apparent molecular size is based on migration in SDS-PAGE. The difference between expected and apparent molecular size is due to the conformation of the PspA fragment.

The proline and repeats/anchor regions (see FIG. 1) were deleted and the resulting protein was unable to attach to cell due to their absence. The unattached protein then may be isolated from culture supernatants, as described below.

By directing the insertion to different points in the PspA gene, different lengths of truncated, non-attached PspA protein derivatives can be produced, as seen in FIG. 7.

STRAINS, PLASMIDS AND PROBES

In the Examples which follow as well as in the accompanying drawings, reference is made to certain plasmids and bacterial strains transformed by such plasmids as well as vector DNA segments, some of which have been deposited with American Type Culture Collection (ATCC), 12301 Parklawn Drive, Rockville Md. 20852 and all of which are fully described herein. The following Table II provides a summary of such materials.

                                      TABLE II                                     __________________________________________________________________________     Identification                                                                       Type      Description                                                                              Deposit                                                                               Location                                      __________________________________________________________________________     JY4313                                                                               E. coli strain                                                                           PspA DNA  ATCC 68529                                                                            Example 1                                     JY2008                                                                               S. pneumomiae strain                                                                     PspA fragment 43 kDa                                                                     ATCC 55143                                                                            Example 1                                     JY4306                                                                               E. coli strain                                                                           PspA fragment 43 kDa                                                                     ATCC 68522                                                                            Example 3                                     JY4310          PspA fragment 21 kDa                                                                     None   FIG. 7                                        JY4285          PspA fragment 18 kDa                                                                     None   FIG. 7                                        pJY4163                                                                              Plasmid   Expression plasmid                                                             used for expression                                                            of PspA -CTB fusion                                                            protein (29 kDa)                                                                         None   Example 6                                     JY4323                                                                               DNA probe HindIII-KpaI segment                                                                     None   Example 9                                     JY4306                                                                               DNA probe HindIII-Dra-I segment                                                                    None   Example 9                                     JY4262                                                                               DNA probe BclI-Bst-NI segment                                                                      None   Example 9                                     __________________________________________________________________________

The pneumococcal strain JY2008 was grown in 6 liters of a chemically defined medium (see Inf. Imm. 27:444) supplemented with 0.10% choline chloride, 0.075% L-cysteine hydrochloride and 0.25% NaHCO₃.The supernatant fluid of the mid-log phase culture of JY2008 was harvested using a 0.22 μm membrane tangential flow filter and concentrated 60 fold.

Introduction of the plasmid pKSD300 into the unmodified D39 strain similarly yielded the 43 kD lo truncated PspA protein. Introduction of the plasmid pKSD300 into the type 3 S.pneumoniae strain WU2 (PspA protein approximately 92 kD) yielded, upon growth of the organism, a non-attached truncated PspA protein of approximately 46 kD molecule size.

Example 2

This Example illustrates the purification of PspA.

The concentrated supernatant fluid, produced as described in Example l, was washed in 0.1 M PBS, pH 7.2, and ultracentrifuged at 196,000 ×g. The supernatant fluid was diluted 1:5 in 20 mM L-histidine buffer-NaCl, the pH adjusted to 6.0 and the injected into a DEAE-fibered Isonet-D2 an ion exchange column.

A stepwise NaCl gradient from 80 mM to 2 M was applied to the column and PspA-containing fractions (0.32 to 0.64 M ionic strength) were pooled and separated on an SDS-polyacrylamide gel. The proteins on a representative section of the gel were stained with comassie Blue R-250 to identify PspA. The fraction containing PspA was excised from the remainder of the SDS-gel and electroeluted from the excised gel. The eluted protein was precipitated in a 50:50 methanol:acetone solvent and resuspended in PBS. Purity of product was confirmed by silver staining and Western Immunoblotting with mAb Xi126 (IgG 2b, k, see McDaniel et al (I), supra).

Example 3

This Example illustrates the isolation of PspA from the periplasmic space of Escherichia coli.

Isolation from the periplasmic space of E. coli was accomplished by standard techniques. E. coli strain JY4306 (which produces the 43 kDa N-terminal fragment of PspA, the amino acid sequence of which is shown in FIG. 3 SEQ ID NO:2. This strain was deposited with ATCC on Jan. 31, 1991 under accession number 68522) was washed in buffered saline, incubated in 20% sucrose, 10 mM EDTA, 25 mM Tris pH 7.7 for 10 minutes at 0° C. The cells then were spun at 400 ×g for 10 minutes at 0° C. All supernatant was removed from the pellet and the pellet was resuspended rapidly in about 100 volumes of 4° C. water. After 10 minutes the suspension was centrifuged at 4,000 ×g for 10 minutes at 4° C. The pellet was discarded and the supernatant, which contained the PspA was saved. Concentration of the supernatant was by standard procedures such as concentration against solid sucrose or ultrafiltration. Purification of the protein isolated from E. coli proceeded by the same chromatography techniques used for the isolated of the 43 kDa (truncated) PspA from the media of growing pneumococci.

Example 4

This Example illustrates the immunogenic properties of the PspA protein.

Sixteen 7-week old CBA/N mice carrying the Xid mutation (Jackson Laboratories, Bar Harbor, Me.) were bled via the periorbital sinus to establish pre-exposure levels of antibody to PspA. Purified PspA, prepared as described in Example 2, was emulsified in complete Freund's adjuvant and injected subcutaneously into the inguinal and axillary regions, delivering approximately 5 μg of protein per mouse. Fourteen days later, the mice were injected intraperitoneally with 5 μg of PspA, prepared as described in Example 2. Control mice were immunized via the same routes with sterile SDS buffer. Seven days after the last immunization, all mice were bled via the periorbital sinus and were challenged intravenously with 300 CFU of the type 3 strain WU2, grown as described in Example 1.

Preimmunization and prechallenge sera were analyzed by Western immunoblots to establish baseline and postimmunization response to the truncated protein. The PspA of strain WU2 was electrophoresed and transferred to nitrocellulose membranes. The membranes were separated into strips and probed with the appropriate mouse antisera at a 1:50 dilution for 2 hours, incubated with biotinylated goat anti-mouse immunoglobulin for 1 hr. washed and incubated with Strepavidin-conjugated phosphatase. The membranes were developed with 5-bromo-4-chloro-3-indoyl phosphate toludine salt with 0.01% into blue tetrazolium.

Of the eight CBA/N mice immunized with the purified fragment of PspA, all were still alive 14 days after challenge with strain WU2 and none showed any signs of illness following challenge. Of the eight mice immunized with buffer controls, six were dead by two days post challenge, while the two remaining control mice appeared very sick, with ruffled fur, arched back and decreased movement, two to three days following challenge but survived. chi-square analysis indicated that there was a significant difference (P<0.003) in survival between the immunized and control groups.

Preimmunization and prechallenge sera were analyzed by Western immunoblotting. None of the preimmunization sera contained antibody to truncated PSpA. Postimmunization sera from eight of eight mice contained detectable antibodies to PspA, and six mice had very strong anti-PspA reactions. When the challenge strain WU2 was probed with the antisera, all the immunized mice had antibodies that were highly cross-reactive with the WU2 PspA epitopes. No control mice developed antibodies to PspA.

The immunization data is summarized in the following Table III:

                  TABLE III                                                        ______________________________________                                                    Detection of                                                                               Alive at  Alive at                                                 Antibody    2 days post                                                                              14 days post                                  Immunogen  to PspA     challenge challenge                                     ______________________________________                                         Isolated PspA                                                                             8/8         8/8       8/8                                           (Example 2)                                                                    Sterile SDS                                                                               0/8         2/8       2/8                                           (control)                                                                      ______________________________________                                    

As may be seen from the data in Table III, immunization with two 5 μg doses of the purified PspA molecule elicited protection against fatal infection of CBA/N mice and elicited antibodies reactive with the PspA of the challenge strain.

Example 5

This Example illustrates sequencing of the PspA protein.

Purified PspA, prepared as described in Example 2, was electrophoresed through 9% resolving gels containing recrystallized SDS with the Laemmli buffer system (Nature 227:680). The gels were soaked twice in a 10 mM 3-(cyclohexylamino)-i-propanesulfonic acid, pH 11.0, containing 10% methanol for 10 minutes. A polyvinylidene difluoride membrane (PVDF) was wetted completely for several seconds in 100% methanol, then washed in CAPS buffer for 10 min. PspA was electrotransferred to the PVDF membrane in CAPS buffer at 0.5 A f or 1 hr. After transfer, the membrane was washed two times in deionized water for 5 min, and stained with 0.1% Coomassie Blue R-250 in 50% methanol for 20 minutes. The section of the membrane containing PspA was excised and destained in 40% methanol and 10% acetic acid for 5 min. The membrane was cut into small segments and stored in sterile Eppendorf tubes until sequencing.

The isolated PspA was sequenced directly from the PVDF membranes. FIG. 2 SEQ ID NO:3 depicts the N-terminal 45 residue amino acid sequence and FIG. 5 depicts the amino acid sequence for the whole alpha-helical region. The DNA sequence of the whole pspA gene and the deduced amino acid sequence for the PspA protein are shown in FIG. 3A-B SEQ ID NO:2.

Example 6

This Example illustrates the use of the PSPA 5'-sequence and/or the PspA N-terminal region to serve as an expression and leader sequence for expressing and/or excreting/secreting heterologous proteins from S.pneumoniae and E.coli. In this Example, there is described the expression of the N-terminal of the PspA protein fused to the B-subunit of cholera toxin (CTB) through a genetic fusion and the excretion of the fused protein from pneumococci and its secretion into the periplasmic space of E.coli.

A fusion protein consisting of CTB and the N-terminal half of PspA was constructed and expressed in E.coli. The HindIII/Dral pspA gene fragment used contained all the pspA transcription and translation initiation signals and the PspA signal peptide leader sequence for transport across the cell membrane. The mature PspA encoded by this fragment is predicted to be a product of 29 kDa (observed molecular weight of 42 kDa), encompassing more than 90% of the α-hemical coiled-coil domain. The CTB fragment used lacked transcription and translation initiation signals. Expression from pspA promoter through pspA and then in-frame translational readthrough into the CTB-encoding gene ctxB resulted in production of a 12 kDa CTB product fused to the upstream PspA product. The PspA-CTB fusion protein was stably expressed in both high and low copy number plasmids (pUC18, more than 100 copies/cell; pJY4163, about 15 to 30 copies/cell) in E.coli.

The fusion products were of the expected size (about 54 kDa) and reacted with antibody to both PspA and CTB. That the CTB product retained its functionality was demonstrated by the ability of the fusion protein to bind ganglioside GM₁, a property of CTB.

The high level of expression of the fusion product apparently resulted in a reduced rate of processing and/or conformational changes that prevented the protein from being completely transported to the periplasm. However, in the lower copy number construct, about 60% of the fusion protein was localized in the periplasm, where large quantities were readily released from E. coli by osmotic shock.

In addition to expression in E.coli, the fusion protein also was expressed in S.pneumoniae by transformation of the low copy number construct into the avirulent S.pneumaniae Rx1 to generate an insertion-duplication mutant. In this way, the gene encoding the fusion protein was integrated into the S.pneumoniae chromosome, from which it was stably expressed. As in the case of Example 1, the truncated PspA molecule lacking the attachment/anchor region, this time in the form of the PspA-CTB fusion protein, was excreted into the culture supernatant. The fusion protein product was of the expected molecular size (54 kDa), reacted with antibody to PspA and CTB, and bound G_(M1).

Example 7

This Example illustrates the use of PspA attachment or anchor region to permit expression of heterologous proteins on the surface of S.pneumoniae or other bacteria in which the attachment/anchor sequence is functional in particular the expression of a PspA-CTB (cholera toxin B subunit) fusion expressed on the surface of pneumococci.

The N-terminal encoding region of PspA, including its transcription and translation initiation signals and its signal peptide leader sequence, is linked via a translationally in-frame genetic fusion to the CTB-encoding ctxB fragment that lacks transcription and translation initiation and termination signals. This sequence is followed in-frame by the PspA attachment/anchor domain, including part or all of the proline, repeat and C-terminal domains. The resulting fusion protein is directed to the outside of the cell via the PspA leader sequence, which is cleaned following transport across the membrane, and then attached to cell by the PspA attachment/anchor sequence. The heterologous protein, located between the two PspA fragments is expressed on the outside surface of the membrane and, in S.pneumoniae, on the surface of the cell.

Example 8

This Example illustrates the expression of truncated and full length PspA by the Mycobacterium tuberculosis strain Bacille Calmette-Guerin (BCG).

BCG was chromosomally modified to incorporate the pspA gene coding for the truncated PspA protein. The 43 kDa truncated PspA protein was expressed from the modified BCG to approximately 15% of total BCG protein. This result was achieved with an expression vector construct carrying the pspA gene segment encoding the 43 kDa region without its 5'-secretion signal. Expression was only about 1% of BCG(3 protein when the PspA or mycobacterial signal sequences were included. In either case, a significant portion of the expressed PspA was excreted into the medium. Expression of the 43 kDa PspA protein in a fusion with the mycobacterial lipoprotein signal sequence resulted in the expression of the recombinant PspA in the membrane fraction of BCG.

This latter result suggested that the fusion of the lipoprotein signal sequence resulted in acylation of the recombinant PspA. Fluorescent activated cell sorting with fluorochrome-conjugated monoclonal antibodies to PspA demonstrated expression of PspA on the surface of these bacteria.

Example 9

This Example illustrates the close homology of portions of the pspA gene among different strains of pneumococci and the potential that such homology may be useful for molecular (DNA) approaches to detect pneumococci in tissues, body fluids and/or secretions and to identify pneumococci grown from patient samples.

Three DNA probes were employed, namely full length pspA, JY4323 (N-terminal HindIII to C-terminal KpnI) , the N-terminal half of pspA, JY4306 (N-terminal HindIII to DraI at position 996 (see FIG. 3 SEQ ID NO:1) and most of the proline and repeat regions, JY4262 (BclI at position 1221 to BstNI at position 1832). Under stringency conditions requiring 95% identity, probes JY4323 and JY4262 reacted with cells of over 200 independent isolates of S.pneumoniae by Southern blot.

When the chromosomal DNA was cut with HindIII, there generally was observed that each of these probes detected two discrete bands whose exact size was dependent on the strain examined. In Rx1 pneumococci, the two bands were 4.0 and 9. 1 kb. The 4.0 kb band corresponded to pspA and was altered or absent in PspA mutants. The other band shares some homology with the coding regions for both the N-terminal and C-terminal halves of PspA but is not affected by pspA mutations. The JY4323 and JY4262 probes failed to react with another gram positive bacterium, Streptococcus pyogenes, and a gram negative bacterium, Salmonella typhimurium. The N-terminal probe, JY4306, recognized about one-third of the strains of pneumococci tested.

These results indicate that a sequence included in the proline/repeat region is shared by all strains of pneumococci and apparently not by other bacterial species. Sequences in the N-terminal half of the molecule appear to be more variable.

Example 10

This Example illustrates the detection and determination of the location of epitopes in the α-helical N-terminal region of PspA.

Monoclonal antibodies protective against pneumococcal infection in a mouse model, denoted by an asterisk in FIGS. 5, 6 and 7, were used to determine the location of epitopes for each antibody in the α-helical N-terminal region of PspA. The sites were mapped to fragments of PspA. The results are illustrated in FIGS. 5 to 7, with FIG. 5 showing the deduced amino acid sequence for the N-terminal region of PspA and the general location of epitopes recognized by monoclonal antibodies, FIG. 6 showing antibody reactivity with PspA fragments produced by various pspA gene segments, and FIG. 7 showing the mapped location of epitopes in the PspA fragments produced by the different pspA gene segments.

Numbers 138, 193 and 261 in FIG. 5 indicate break positions in the PspA fragments used to map the location of epitopes detected by monoclonal antibodies Xi1526, Xi126, XiR35, XiR38, XiR1224, XiR16, Xi64, XiR278, Xi1325 and Xi1323. The asterisk (*) after some of the antibodies denotes those which are able to protect against fatal pneumococcal infection with strain WU2 pneumococci.

In addition, the vertical lines to the right of the Figure indicate those areas predicted to have coiled-coil α-helical structure. The divisions to the left of the Figure indicate the mapped location of the epitopes for each antibody.

SUMMARY OF DISCLOSURE

In summary of this disclosure, the present invention relates to a truncated PspA molecule capable of eliciting an immunoprotective response and hence containing the protective epitopes of PspA protein. Modifications are possible within the scope of this invention.

SEQUENCE LISTINGS

Submitted with this application are Sequence Listings, identified as follows:

(a) SEQ ID No: 1 shows the nucleotide sequence and derived amino acid sequence for the HindIII-KpnI fragment containing the complete pspa gene, as shown in FIG. 3.

(b) SEQ ID No: 2 shows the derived amino acid sequence for the PspA protein, as shown in FIG. 3.

(c) SEQ ID No: 3 shows the N-terminal amino acid sequence of PspA, as shown in FIG. 2.

(d) SEQ ID No: 4 shows the derived amino acid sequence for the N-terminal region of PspA as shown in FIG. 5.

(e) SEQ ID No: 5 shows the nucleotide sequence for primer LSM1.

(f) SEQ ID No: 6 shows the nucleotide sequence for primer LSM2.

    __________________________________________________________________________     #             SEQUENCE LISTING                                                 - (1) GENERAL INFORMATION:                                                     -    (iii) NUMBER OF SEQUENCES: 10                                             - (2) INFORMATION FOR SEQ ID NO:1:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 2085 base                                                          (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: double                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        -    (iii) HYPOTHETICAL: NO                                                    -     (iv) ANTI-SENSE: NO                                                      -     (vi) ORIGINAL SOURCE:                                                    #pneumoniae Rx1TRAIN: Streptococcus                                            -    (vii) IMMEDIATE SOURCE:                                                             (B) CLONE: JY2008                                                    -     (ix) FEATURE:                                                                      (A) NAME/KEY: intron                                                           (B) LOCATION: 1..2085                                                -     (ix) FEATURE:                                                                      (A) NAME/KEY: CDS                                                              (B) LOCATION: join(127..19 - #83, 1987..1992, 1996..2007, 2011                      ..2025, 2 - #029..2031, 2035..2085)                             -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:                                  - AAGCTTATGA TATAGAAATT TGTAACAAAA ATGTAATATA AAACACTTGA CA - #AATATTTA          60                                                                           - CGGAGGAGGC TTATACTTAA TATAAGTATA GTCTGAAAAT GACTATCAGA AA - #AGAGGTAA         120                                                                           #AGT CTA GCC AGC GTC       168TG ATT TTA ACA                                          Met Asn Lys Lys Lys Met Il - #e Leu Thr Ser Leu Ala Ser Val             #      10                                                                      - GCT ATC TTA GGG GCT GGT TTT GTT GCG TCT CA - #G CCT ACT GTT GTA AGA           216                                                                           Ala Ile Leu Gly Ala Gly Phe Val Ala Ser Gl - #n Pro Thr Val Val Arg            # 30                                                                           - GCA GAA GAA TCT CCC GTA GCC AGT CAG TCT AA - #A GCT GAG AAA GAC TAT           264                                                                           Ala Glu Glu Ser Pro Val Ala Ser Gln Ser Ly - #s Ala Glu Lys Asp Tyr            #                 45                                                           - GAT GCA GCG AAG AAA GAT GCT AAG AAT GCG AA - #A AAA GCA GTA GAA GAT           312                                                                           Asp Ala Ala Lys Lys Asp Ala Lys Asn Ala Ly - #s Lys Ala Val Glu Asp            #             60                                                               - GCT CAA AAG GCT TTA GAT GAT GCA AAA GCT GC - #T CAG AAA AAA TAT GAC           360                                                                           Ala Gln Lys Ala Leu Asp Asp Ala Lys Ala Al - #a Gln Lys Lys Tyr Asp            #         75                                                                   - GAG GAT CAG AAG AAA ACT GAG GAG AAA GCC GC - #G CTA GAA AAA GCA GCG           408                                                                           Glu Asp Gln Lys Lys Thr Glu Glu Lys Ala Al - #a Leu Glu Lys Ala Ala            #     90                                                                       - TCT GAA GAG ATG GAT AAG GCA GTG GCA GCA GT - #T CAA CAA GCG TAT CTA           456                                                                           Ser Glu Glu Met Asp Lys Ala Val Ala Ala Va - #l Gln Gln Ala Tyr Leu            #110                                                                           - GCC TAT CAA CAA GCT ACA GAC AAA GCC GCA AA - #A GAC GCA GCA GAT AAG           504                                                                           Ala Tyr Gln Gln Ala Thr Asp Lys Ala Ala Ly - #s Asp Ala Ala Asp Lys            #               125                                                            - ATG ATA GAT GAA GCT AAG AAA CGC GAA GAA GA - #G GCA AAA ACT AAA TTT           552                                                                           Met Ile Asp Glu Ala Lys Lys Arg Glu Glu Gl - #u Ala Lys Thr Lys Phe            #           140                                                                - AAT ACT GTT CGA GCA ATG GTA GTT CCT GAG CC - #A GAG CAG TTG GCT GAG           600                                                                           Asn Thr Val Arg Ala Met Val Val Pro Glu Pr - #o Glu Gln Leu Ala Glu            #       155                                                                    - ACT AAG AAA AAA TCA GAA GAA GCT AAA CAA AA - #A GCA CCA GAA CTT ACT           648                                                                           Thr Lys Lys Lys Ser Glu Glu Ala Lys Gln Ly - #s Ala Pro Glu Leu Thr            #   170                                                                        - AAA AAA CTA GAA GAA GCT AAA GCA AAA TTA GA - #A GAG GCT GAG AAA AAA           696                                                                           Lys Lys Leu Glu Glu Ala Lys Ala Lys Leu Gl - #u Glu Ala Glu Lys Lys            175                 1 - #80                 1 - #85                 1 -        #90                                                                            - GCT ACT GAA GCC AAA CAA AAA GTG GAT GCT GA - #A GAA GTC GCT CCT CAA           744                                                                           Ala Thr Glu Ala Lys Gln Lys Val Asp Ala Gl - #u Glu Val Ala Pro Gln            #               205                                                            - GCT AAA ATC GCT GAA TTG GAA AAT CAA GTT CA - #T AGA CTA GAA CAA GAG           792                                                                           Ala Lys Ile Ala Glu Leu Glu Asn Gln Val Hi - #s Arg Leu Glu Gln Glu            #           220                                                                - CTC AAA GAG ATT GAT GAG TCT GAA TCA GAA GA - #T TAT GCT AAA GAA GGT           840                                                                           Leu Lys Glu Ile Asp Glu Ser Glu Ser Glu As - #p Tyr Ala Lys Glu Gly            #       235                                                                    - TTC CGT GCT CCT CTT CAA TCT AAA TTG GAT GC - #C AAA AAA GCT AAA CTA           888                                                                           Phe Arg Ala Pro Leu Gln Ser Lys Leu Asp Al - #a Lys Lys Ala Lys Leu            #   250                                                                        - TCA AAA CTT GAA GAG TTA AGT GAT AAG ATT GA - #T GAG TTA GAC GCT GAA           936                                                                           Ser Lys Leu Glu Glu Leu Ser Asp Lys Ile As - #p Glu Leu Asp Ala Glu            255                 2 - #60                 2 - #65                 2 -        #70                                                                            - ATT GCA AAA CTT GAA GAT CAA CTT AAA GCT GC - #T GAA GAA AAC AAT AAT           984                                                                           Ile Ala Lys Leu Glu Asp Gln Leu Lys Ala Al - #a Glu Glu Asn Asn Asn            #               285                                                            - GTA GAA GAC TAC TTT AAA GAA GGT TTA GAG AA - #A ACT ATT GCT GCT AAA          1032                                                                           Val Glu Asp Tyr Phe Lys Glu Gly Leu Glu Ly - #s Thr Ile Ala Ala Lys            #           300                                                                - AAA GCT GAA TTA GAA AAA ACT GAA GCT GAC CT - #T AAG AAA GCA GTT AAT          1080                                                                           Lys Ala Glu Leu Glu Lys Thr Glu Ala Asp Le - #u Lys Lys Ala Val Asn            #       315                                                                    - GAG CCA GAA AAA CCA GCT CCA GCT CCA GAA AC - #T CCA GCC CCA GAA GCA          1128                                                                           Glu Pro Glu Lys Pro Ala Pro Ala Pro Glu Th - #r Pro Ala Pro Glu Ala            #   330                                                                        - CCA GCT GAA CAA CCA AAA CCA GCG CCG GCT CC - #T CAA CCA GCT CCC GCA          1176                                                                           Pro Ala Glu Gln Pro Lys Pro Ala Pro Ala Pr - #o Gln Pro Ala Pro Ala            335                 3 - #40                 3 - #45                 3 -        #50                                                                            - CCA AAA CCA GAG AAG CCA GCT GAA CAA CCA AA - #A CCA GAA AAA ACA GAT          1224                                                                           Pro Lys Pro Glu Lys Pro Ala Glu Gln Pro Ly - #s Pro Glu Lys Thr Asp            #               365                                                            - GAT CAA CAA GCT GAA GAA GAC TAT GCT CGT AG - #A TCA GAA GAA GAA TAT          1272                                                                           Asp Gln Gln Ala Glu Glu Asp Tyr Ala Arg Ar - #g Ser Glu Glu Glu Tyr            #           380                                                                - AAT CGC TTG ACT CAA CAG CAA CCG CCA AAA GC - #T GAA AAA CCA GCT CCT          1320                                                                           Asn Arg Leu Thr Gln Gln Gln Pro Pro Lys Al - #a Glu Lys Pro Ala Pro            #       395                                                                    - GCA CCA AAA ACA GGC TGG AAA CAA GAA AAC GG - #T ATG TGG TAC TTC TAC          1368                                                                           Ala Pro Lys Thr Gly Trp Lys Gln Glu Asn Gl - #y Met Trp Tyr Phe Tyr            #   410                                                                        - AAT ACT GAT GGT TCA ATG GCG ACA GGA TGG CT - #C CAA AAC AAC GGT TCA          1416                                                                           Asn Thr Asp Gly Ser Met Ala Thr Gly Trp Le - #u Gln Asn Asn Gly Ser            415                 4 - #20                 4 - #25                 4 -        #30                                                                            - TGG TAC TAC CTC AAC AGC AAT GGT GCT ATG GC - #T ACA GGT TGG CTC CAA          1464                                                                           Trp Tyr Tyr Leu Asn Ser Asn Gly Ala Met Al - #a Thr Gly Trp Leu Gln            #               445                                                            - TAC AAT GGT TCA TGG TAT TAC CTC AAC GCT AA - #C GGC GCT ATG GCA ACA          1512                                                                           Tyr Asn Gly Ser Trp Tyr Tyr Leu Asn Ala As - #n Gly Ala Met Ala Thr            #           460                                                                - GGT TGG GCT AAA GTC AAC GGT TCA TGG TAC TA - #C CTC AAC GCT AAT GGT          1560                                                                           Gly Trp Ala Lys Val Asn Gly Ser Trp Tyr Ty - #r Leu Asn Ala Asn Gly            #       475                                                                    - GCT ATG GCT ACA GGT TGG CTC CAA TAC AAC GG - #T TCA TGG TAT TAC CTC          1608                                                                           Ala Met Ala Thr Gly Trp Leu Gln Tyr Asn Gl - #y Ser Trp Tyr Tyr Leu            #   490                                                                        - AAC GCT AAC GGC GCT ATG GCA ACA GGT TGG GC - #T AAA GTC AAC GGT TCA          1656                                                                           Asn Ala Asn Gly Ala Met Ala Thr Gly Trp Al - #a Lys Val Asn Gly Ser            495                 5 - #00                 5 - #05                 5 -        #10                                                                            - TGG TAC TAC CTC AAC GCT AAT GGT GCT ATG GC - #T ACA GGT TGG CTC CAA          1704                                                                           Trp Tyr Tyr Leu Asn Ala Asn Gly Ala Met Al - #a Thr Gly Trp Leu Gln            #               525                                                            - TAC AAC GGT TCA TGG TAC TAC CTC AAC GCT AA - #C GGT GCT ATG GCT ACA          1752                                                                           Tyr Asn Gly Ser Trp Tyr Tyr Leu Asn Ala As - #n Gly Ala Met Ala Thr            #           540                                                                - GGT TGG GCT AAA GTC AAC GGT TCA TGG TAC TA - #C CTC AAC GCT AAT GGT          1800                                                                           Gly Trp Ala Lys Val Asn Gly Ser Trp Tyr Ty - #r Leu Asn Ala Asn Gly            #       555                                                                    - GCT ATG GCA ACA GGT TGG GTG AAA GAT GGA GA - #T ACC TGG TAC TAT CTT          1848                                                                           Ala Met Ala Thr Gly Trp Val Lys Asp Gly As - #p Thr Trp Tyr Tyr Leu            #   570                                                                        - GAA GCA TCA GGT GCT ATG AAA GCA AGC CAA TG - #G TTC AAA GTA TCA GAT          1896                                                                           Glu Ala Ser Gly Ala Met Lys Ala Ser Gln Tr - #p Phe Lys Val Ser Asp            575                 5 - #80                 5 - #85                 5 -        #90                                                                            - AAA TGG TAC TAT GTC AAT GGT TTA GGT GCC CT - #T GCA GTC AAC ACA ACT          1944                                                                           Lys Trp Tyr Tyr Val Asn Gly Leu Gly Ala Le - #u Ala Val Asn Thr Thr            #               605                                                            - GTA GAT GGC TAT AAA GTC AAT GCC AAT GGT GA - #A TGG GTT TAA GCC GAT          1992                                                                           Val Asp Gly Tyr Lys Val Asn Ala Asn Gly Gl - #u Trp Val     Ala Asp            #               620                                                            - TAA ATT AAA GCA TGT TAA GAA CAT TTG ACA TT - #T TAA TTT TGA AAC AAA          2040                                                                           #Leu Thr Phe     Phe     Asn Lys                                               # 630                                                                          - GAT AAG GTT CGA TTG AAT AGA TTT ATG TTC GT - #A TTC TTT AGG TAC              2085                                                                           Asp Lys Val Arg Leu Asn Arg Phe Met Phe Va - #l Phe Phe Arg Tyr                #   645                                                                        - (2) INFORMATION FOR SEQ ID NO:2:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 648 amino                                                          (B) TYPE: amino acid                                                           (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: protein                                              -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:                                  - Met Asn Lys Lys Lys Met Ile Leu Thr Ser Le - #u Ala Ser Val Ala Ile          #                 15                                                           - Leu Gly Ala Gly Phe Val Ala Ser Gln Pro Th - #r Val Val Arg Ala Glu          #             30                                                               - Glu Ser Pro Val Ala Ser Gln Ser Lys Ala Gl - #u Lys Asp Tyr Asp Ala          #         45                                                                   - Ala Lys Lys Asp Ala Lys Asn Ala Lys Lys Al - #a Val Glu Asp Ala Gln          #     60                                                                       - Lys Ala Leu Asp Asp Ala Lys Ala Ala Gln Ly - #s Lys Tyr Asp Glu Asp          # 80                                                                           - Gln Lys Lys Thr Glu Glu Lys Ala Ala Leu Gl - #u Lys Ala Ala Ser Glu          #                 95                                                           - Glu Met Asp Lys Ala Val Ala Ala Val Gln Gl - #n Ala Tyr Leu Ala Tyr          #           110                                                                - Gln Gln Ala Thr Asp Lys Ala Ala Lys Asp Al - #a Ala Asp Lys Met Ile          #       125                                                                    - Asp Glu Ala Lys Lys Arg Glu Glu Glu Ala Ly - #s Thr Lys Phe Asn Thr          #   140                                                                        - Val Arg Ala Met Val Val Pro Glu Pro Glu Gl - #n Leu Ala Glu Thr Lys          145                 1 - #50                 1 - #55                 1 -        #60                                                                            - Lys Lys Ser Glu Glu Ala Lys Gln Lys Ala Pr - #o Glu Leu Thr Lys Lys          #               175                                                            - Leu Glu Glu Ala Lys Ala Lys Leu Glu Glu Al - #a Glu Lys Lys Ala Thr          #           190                                                                - Glu Ala Lys Gln Lys Val Asp Ala Glu Glu Va - #l Ala Pro Gln Ala Lys          #       205                                                                    - Ile Ala Glu Leu Glu Asn Gln Val His Arg Le - #u Glu Gln Glu Leu Lys          #   220                                                                        - Glu Ile Asp Glu Ser Glu Ser Glu Asp Tyr Al - #a Lys Glu Gly Phe Arg          225                 2 - #30                 2 - #35                 2 -        #40                                                                            - Ala Pro Leu Gln Ser Lys Leu Asp Ala Lys Ly - #s Ala Lys Leu Ser Lys          #               255                                                            - Leu Glu Glu Leu Ser Asp Lys Ile Asp Glu Le - #u Asp Ala Glu Ile Ala          #           270                                                                - Lys Leu Glu Asp Gln Leu Lys Ala Ala Glu Gl - #u Asn Asn Asn Val Glu          #       285                                                                    - Asp Tyr Phe Lys Glu Gly Leu Glu Lys Thr Il - #e Ala Ala Lys Lys Ala          #   300                                                                        - Glu Leu Glu Lys Thr Glu Ala Asp Leu Lys Ly - #s Ala Val Asn Glu Pro          305                 3 - #10                 3 - #15                 3 -        #20                                                                            - Glu Lys Pro Ala Pro Ala Pro Glu Thr Pro Al - #a Pro Glu Ala Pro Ala          #               335                                                            - Glu Gln Pro Lys Pro Ala Pro Ala Pro Gln Pr - #o Ala Pro Ala Pro Lys          #           350                                                                - Pro Glu Lys Pro Ala Glu Gln Pro Lys Pro Gl - #u Lys Thr Asp Asp Gln          #       365                                                                    - Gln Ala Glu Glu Asp Tyr Ala Arg Arg Ser Gl - #u Glu Glu Tyr Asn Arg          #   380                                                                        - Leu Thr Gln Gln Gln Pro Pro Lys Ala Glu Ly - #s Pro Ala Pro Ala Pro          385                 3 - #90                 3 - #95                 4 -        #00                                                                            - Lys Thr Gly Trp Lys Gln Glu Asn Gly Met Tr - #p Tyr Phe Tyr Asn Thr          #               415                                                            - Asp Gly Ser Met Ala Thr Gly Trp Leu Gln As - #n Asn Gly Ser Trp Tyr          #           430                                                                - Tyr Leu Asn Ser Asn Gly Ala Met Ala Thr Gl - #y Trp Leu Gln Tyr Asn          #       445                                                                    - Gly Ser Trp Tyr Tyr Leu Asn Ala Asn Gly Al - #a Met Ala Thr Gly Trp          #   460                                                                        - Ala Lys Val Asn Gly Ser Trp Tyr Tyr Leu As - #n Ala Asn Gly Ala Met          465                 4 - #70                 4 - #75                 4 -        #80                                                                            - Ala Thr Gly Trp Leu Gln Tyr Asn Gly Ser Tr - #p Tyr Tyr Leu Asn Ala          #               495                                                            - Asn Gly Ala Met Ala Thr Gly Trp Ala Lys Va - #l Asn Gly Ser Trp Tyr          #           510                                                                - Tyr Leu Asn Ala Asn Gly Ala Met Ala Thr Gl - #y Trp Leu Gln Tyr Asn          #       525                                                                    - Gly Ser Trp Tyr Tyr Leu Asn Ala Asn Gly Al - #a Met Ala Thr Gly Trp          #   540                                                                        - Ala Lys Val Asn Gly Ser Trp Tyr Tyr Leu As - #n Ala Asn Gly Ala Met          545                 5 - #50                 5 - #55                 5 -        #60                                                                            - Ala Thr Gly Trp Val Lys Asp Gly Asp Thr Tr - #p Tyr Tyr Leu Glu Ala          #               575                                                            - Ser Gly Ala Met Lys Ala Ser Gln Trp Phe Ly - #s Val Ser Asp Lys Trp          #           590                                                                - Tyr Tyr Val Asn Gly Leu Gly Ala Leu Ala Va - #l Asn Thr Thr Val Asp          #       605                                                                    - Gly Tyr Lys Val Asn Ala Asn Gly Glu Trp Va - #l Ala Asp Ile Lys Ala          #   620                                                                        - Cys Glu His Leu Thr Phe Phe Asn Lys Asp Ly - #s Val Arg Leu Asn Arg          625                 6 - #30                 6 - #35                 6 -        #40                                                                            - Phe Met Phe Val Phe Phe Arg Tyr                                                              645                                                            - (2) INFORMATION FOR SEQ ID NO:3:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 619 amino                                                          (B) TYPE: amino acid                                                           (C) STRANDEDNESS: Not R - #elevant                                             (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: amino acid                                           -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:                                  - Met Asn Lys Lys Lys Met Ile Leu Thr Ser Le - #u Ala Ser Val Ala Ile          #                15                                                            - Leu Gly Ala Gly Phe Val Ala Ser Gln Pro Th - #r Val Val Arg Ala Glu          #            30                                                                - Glu Ser Pro Val Ala Ser Gln Ser Lys Ala Gl - #u Lys Asp Tyr Asp Ala          #        45                                                                    - Ala Lys Lys Asp Ala Lys Asn Ala Lys Lys Al - #a Val Glu Asp Ala Gln          #    60                                                                        - Lys Ala Leu Asp Asp Ala Lys Ala Ala Gln Ly - #s Lys Tyr Asp Glu Asp          #80                                                                            - Gln Lys Lys Thr Glu Glu Lys Ala Ala Leu Gl - #u Lys Ala Ala Ser Glu          #                95                                                            - Glu Met Asp Lys Ala Val Ala Ala Val Gln Gl - #n Ala Tyr Leu Ala Tyr          #           110                                                                - Gln Gln Ala Thr Asp Lys Ala Ala Lys Asp Al - #a Ala Asp Lys Met Ile          #       125                                                                    - Asp Glu Ala Lys Lys Arg Glu Glu Glu Ala Ly - #s Thr Lys Phe Asn Thr          #   140                                                                        - Val Arg Ala Met Val Val Pro Glu Pro Glu Gl - #n Leu Ala Glu Thr Lys          145                 1 - #50                 1 - #55                 1 -        #60                                                                            - Lys Lys Ser Glu Glu Ala Lys Gln Lys Ala Pr - #o Glu Leu Thr Lys Lys          #               175                                                            - Leu Glu Glu Ala Lys Ala Lys Leu Glu Glu Al - #a Glu Lys Lys Ala Thr          #           190                                                                - Glu Ala Lys Gln Lys Val Asp Ala Glu Glu Va - #l Ala Pro Gln Ala Lys          #       205                                                                    - Ile Ala Glu Leu Glu Asn Gln Val His Arg Le - #u Glu Gln Glu Leu Lys          #   220                                                                        - Glu Ile Asp Glu Ser Glu Ser Glu Asp Tyr Al - #a Lys Glu Gly Phe Arg          225                 2 - #30                 2 - #35                 2 -        #40                                                                            - Ala Pro Leu Gln Ser Lys Leu Asp Ala Lys Ly - #s Ala Lys Leu Ser Lys          #               255                                                            - Leu Glu Glu Leu Ser Asp Lys Ile Asp Glu Le - #u Asp Ala Glu Ile Ala          #           270                                                                - Lys Leu Glu Asp Gln Leu Lys Ala Ala Glu Gl - #u Asn Asn Asn Val Glu          #       285                                                                    - Asp Tyr Phe Lys Glu Gly Leu Glu Lys Thr Il - #e Ala Ala Lys Lys Ala          #   300                                                                        - Glu Leu Glu Lys Thr Glu Ala Asp Leu Lys Ly - #s Ala Val Asn Glu Pro          305                 3 - #10                 3 - #15                 3 -        #20                                                                            - Glu Lys Pro Ala Pro Ala Pro Glu Thr Pro Al - #a Pro Glu Ala Pro Ala          #               335                                                            - Glu Gln Pro Lys Pro Ala Pro Ala Pro Gln Pr - #o Ala Pro Ala Pro Lys          #           350                                                                - Pro Glu Lys Pro Ala Glu Gln Pro Lys Pro Gl - #u Lys Thr Asp Asp Gln          #       365                                                                    - Gln Ala Glu Glu Asp Tyr Ala Arg Arg Ser Gl - #u Glu Glu Tyr Asn Arg          #   380                                                                        - Leu Thr Gln Gln Gln Pro Pro Lys Ala Glu Ly - #s Pro Ala Pro Ala Pro          385                 3 - #90                 3 - #95                 4 -        #00                                                                            - Lys Thr Gly Trp Lys Gln Glu Asn Gly Met Tr - #p Tyr Phe Tyr Asn Thr          #               415                                                            - Asp Gly Ser Met Ala Thr Gly Trp Leu Gln As - #n Asn Gly Ser Trp Tyr          #           430                                                                - Tyr Leu Asn Ser Asn Gly Ala Met Ala Thr Gl - #y Trp Leu Gln Tyr Asn          #       445                                                                    - Gly Ser Trp Tyr Tyr Leu Asn Ala Asn Gly Al - #a Met Ala Thr Gly Trp          #   460                                                                        - Ala Lys Val Asn Gly Ser Trp Tyr Tyr Leu As - #n Ala Asn Gly Ala Met          465                 4 - #70                 4 - #75                 4 -        #80                                                                            - Ala Thr Gly Trp Leu Gln Tyr Asn Gly Ser Tr - #p Tyr Tyr Leu Asn Ala          #               495                                                            - Asn Gly Ala Met Ala Thr Gly Trp Ala Lys Va - #l Asn Gly Ser Trp Tyr          #           510                                                                - Tyr Leu Asn Ala Asn Gly Ala Met Ala Thr Gl - #y Trp Leu Gln Tyr Asn          #       525                                                                    - Gly Ser Trp Tyr Tyr Leu Asn Ala Asn Gly Al - #a Met Ala Thr Gly Trp          #   540                                                                        - Ala Lys Val Asn Gly Ser Trp Tyr Tyr Leu As - #n Ala Asn Gly Ala Met          545                 5 - #50                 5 - #55                 5 -        #60                                                                            - Ala Thr Gly Trp Val Lys Asp Gly Asp Thr Tr - #p Tyr Tyr Leu Glu Ala          #               575                                                            - Ser Gly Ala Met Lys Ala Ser Gln Trp Phe Ly - #s Val Ser Asp Lys Trp          #           590                                                                - Tyr Tyr Val Asn Gly Leu Gly Ala Leu Ala Va - #l Asn Thr Thr Val Asp          #       605                                                                    - Gly Tyr Lys Val Asn Ala Asn Gly Glu Trp Va - #l                              #   615                                                                        - (2) INFORMATION FOR SEQ ID NO:4:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 45 amino                                                           (B) TYPE: amino acid                                                           (C) STRANDEDNESS: Not R - #elevant                                             (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: amino acid                                           -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:                                  - Glu Glu Ser Pro Val Ala Ser Gln Ser Lys Al - #a Glu Lys Asp Tyr Asp          #                15                                                            - Ala Ala Lys Lys Asp Ala Lys Asn Ala Lys Ly - #s Ala Val Glu Asp Ala          #            30                                                                - Gln Lys Ala Leu Asp Asp Ala Lys Ala Ala Gl - #n Lys Lys                      #        45                                                                    - (2) INFORMATION FOR SEQ ID NO:5:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 289 amino                                                          (B) TYPE: amino acid                                                           (C) STRANDEDNESS: Not R - #elevant                                             (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: amino acid                                           -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:                                  - Glu Glu Ser Pro Val Ala Ser Gln Ser Lys Al - #a Glu Lys Asp Tyr Asp          #                15                                                            - Ala Ala Lys Lys Asp Ala Lys Asn Ala Lys Ly - #s Ala Val Glu Asp Ala          #            30                                                                - Gln Lys Ala Leu Asp Asp Ala Lys Ala Ala Gl - #n Lys Lys Tyr Asp Glu          #        45                                                                    - Asp Gln Lys Lys Thr Glu Glu Lys Ala Ala Le - #u Glu Lys Ala Ala Ser          #    60                                                                        - Glu Glu Met Asp Lys Ala Val Ala Ala Val Gl - #n Gln Ala Tyr Leu Ala          #80                                                                            - Tyr Gln Gln Ala Thr Asp Lys Ala Ala Lys As - #p Ala Ala Asp Lys Met          #                95                                                            - Ile Asp Glu Ala Lys Lys Arg Glu Glu Glu Al - #a Lys Thr Lys Phe Asn          #           110                                                                - Thr Val Arg Ala Met Val Val Pro Glu Pro Gl - #u Gln Leu Ala Glu Thr          #       125                                                                    - Lys Lys Lys Ser Glu Glu Ala Lys Gln Lys Al - #a Pro Glu Leu Thr Lys          #   140                                                                        - Lys Leu Glu Glu Ala Lys Ala Lys Leu Glu Gl - #u Ala Glu Lys Lys Ala          145                 1 - #50                 1 - #55                 1 -        #60                                                                            - Thr Glu Ala Lys Gln Lys Val Asp Ala Glu Gl - #u Val Ala Pro Gln Ala          #               175                                                            - Lys Ile Ala Glu Leu Glu Asn Gln Val His Ar - #g Leu Glu Gln Glu Leu          #           190                                                                - Lys Glu Ile Asp Glu Ser Glu Ser Glu Glu As - #p Tyr Ala Lys Glu Gly          #       205                                                                    - Phe Arg Ala Pro Leu Gln Ser Lys Leu Asp Al - #a Lys Lys Ala Lys Leu          #   220                                                                        - Ser Lys Leu Glu Glu Leu Ser Asp Lys Ile As - #p Glu Leu Asp Ala Glu          225                 2 - #30                 2 - #35                 2 -        #40                                                                            - Ile Ala Lys Leu Glu Asp Gln Leu Lys Ala Al - #a Glu Glu Asn Asn Asn          #               255                                                            - Val Glu Asp Tyr Phe Lys Glu Gly Leu Glu Ly - #s Thr Ile Ala Ala Lys          #           270                                                                - Lys Ala Glu Leu Glu Lys Thr Glu Ala Asp Le - #u Lys Lys Ala Val Asn          #       285                                                                    - Glu                                                                          - (2) INFORMATION FOR SEQ ID NO:6:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 26 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:                                  #              26  CACC AAAAAC                                                 - (2) INFORMATION FOR SEQ ID NO:7:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #pairs    (A) LENGTH: 33 base                                                            (B) TYPE: nucleic acid                                                         (C) STRANDEDNESS: single                                                       (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: DNA (genomic)                                        -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:                                  #         33       AACC CATTCACCAT TGG                                         - (2) INFORMATION FOR SEQ ID NO:8:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 4 amino                                                            (B) TYPE: amino acid                                                           (C) STRANDEDNESS: Not R - #elevant                                             (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: amino acid                                           -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:                                  - Ile Lys Ala Cys                                                              - (2) INFORMATION FOR SEQ ID NO:9:                                             -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 5 amino                                                            (B) TYPE: amino acid                                                           (C) STRANDEDNESS: Not R - #elevant                                             (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: amino acid                                           -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9:                                  - Glu His Leu Thr Phe                                                          1               5                                                              - (2) INFORMATION FOR SEQ ID NO:10:                                            -      (i) SEQUENCE CHARACTERISTICS:                                           #acids    (A) LENGTH: 17 amino                                                           (B) TYPE: amino acid                                                           (C) STRANDEDNESS: Not R - #elevant                                             (D) TOPOLOGY: linear                                                 -     (ii) MOLECULE TYPE: amino acid                                           -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10:                                 - Asn Lys Asp Lys Val Arg Leu Asn Arg Phe Me - #t Phe Val Phe Phe Arg          #                15                                                            - Tyr                                                                          __________________________________________________________________________ 

What we claim is:
 1. An isolated DNA molecule consisting of a nuclaotide sequence coding for an immunoprotective pneumococcal surface protein A (PspA) wherein said PspA comprises the sequence of FIG. 3 (SEQ ID NO: 2).
 2. An isolated DNA molecule consisting of a nucleotide sequence coding for an α-helical coiled coil region of pneumocaccal surface protein A (PspA) wherein said PspA comprises the sequence of FIG. 3 (SEQ ID NO: 2).
 3. An isolated DNA molecule consisting of a nucleotide sequence coding for a proline rich region and repeat region of pneumococcal surface protein A (PspA) wherein said PspA comprises the sequence of FIG. 3 (SEQ ID NO: 2).
 4. An isolated DNA molecule consisting of a nucleotide sequence coding for a truncated form of whole pneumccoccal surface protein A (PspA) wherein said whole PspA comprises the sequence of FIG. 3 (SEQ ID NO: 2), wherein said truncated PspA contains immunoprotective epitopes and has the cell membrane anchor region absent therefrom.
 5. An isolated DNA molecule consisting of a nucleotide sequence coding for a truncated form of whole pneumococcal surface protein A (PspA) wherein said whole PspA comprises the sequence of FIG. 3 (SEQ ID NO: 2) wherein said truncated PspA contains about 50% of the whole PspA protein and has the cell membrane anchor region, the repeats region, and the proline region absent therefrom.
 6. An isolated DNA molecule consisting of a nucleotide sequence coding for a truncated form of whole pneumococcal surface protein A (PspA) said whole PspA comprises the sequence of FIG. 3 (SEQ ID NO: 2), wherein said truncated PspA contains immunoprotective epitopes and about 90% of the whole PspA protein and has the cell anchor region absent therefrom.
 7. A method for forming an immunoprotective truncated pneumococcal surface protein A (PspA), which comprises:incorporating a vector comprising the isolated DNA molecule of claim 4 into a bacterium by transformation whereby said transformed bacterium expresses said DNA molecule, growing said bacterium to effect expression of said truncated PspA protein, and isolating said truncated PspA protein.
 8. The method of claim 7 wherein said transformed bacterium is a Stretococcus pneumoniae strain, said strain is grown in a defined medium to effect expression of the truncated PspA protein into said medium, and the truncated PspA protein is isolated from the medium.
 9. The method of claim 8 wherein said mutated strain is Streptococcus pneumoniae l strain JY2008 (ATCC Accession No. 55143).
 10. The method of claim 7 wherein said transformed bacterium is a Eschoricha coli strain, said strain is grown to effect expression of the truncated PspA protein into the proplasm of said strain, and the truncated PspA protein is isolated from the periplasm of said strain.
 11. The method of claim 10 wherein said strain is Escherichia coli strain JY4306 (ATCC Accession No. 68522).
 12. The method of claim 7 wherein said isolated truncated PspA protein is purified by ion-exchange chromatography.
 13. The method of claim 7 wherein said tranformed bacterium is selected from the group consisting of Streptococcus pneumoniae and Escherichia coli. 